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45 Información general / General information TÍTULO: 3D Modelling in the registration and restoration of a megalithic tomb :TITLE AUTORES: Álvaro RODRÍGUEZ MIRANDA :AUTORS Pablo PÉREZ VIDIELLA Javier FERNÁNDEZ ERASO José Antonio MUJIKA ALUSTIZA José Manuel VALLE MELÓN FECHA: mayo 2017 / May 2017 :DATE NÚMERO: LDGP_art_045 :NUMBER IDIOMA: inglés / English :LANGUAGE
Resumen TÍTULO: El modelado 3D en el registro y la restauración de una tumba megalítica RESUMEN: El presente artículo muestra algunas aplicaciones de las técnicas geomáticas aplicadas a trabajos en los que la excavación y la restauración se realizan de forma simultánea, de forma que la disposición tridimensional del monumento experimenta cambios significativos a lo largo de la intervención.
El artículo repasa diversos trabajos de documentación geométrica y modelado tridimensional desarrollados durante las excavaciones arqueológicas y la restauración de un monumento megalítico –dolmen del Alto de la Huesera- en el periodo 2010 a 2014.
Las actividades descritas abarcan un amplio rango de objetivos, incluyendo el replanteo de la cuadrícula de excavación, el registro geométrico de los enterramientos, el modelado tridimensional de las losas y túmulo circundante, la visualización virtual y prueba de posibles reconstrucciones antes de acometer la recolocación física de los elementos del dolmen, así como la clasificación y el archivo de la información con el fin de mantener la trazabilidad de las tareas realizadas durante este periodo. DESCRIPTORES dolmen, restitución fotogramétrica, Structure from Motion (SfM), modelo 3D NATURALES: incremental, modelo 3D multitemporal (modelo 4D) DESCRIPTORES (Procedentes del Tesauro UNESCO [http://databases.unesco.org/thessp/]) CONTROLADOS: Patrimonio Cultural, Restauración, Prehistoria, Fotogrametría, Infografía
Abstract TITLE: 3D Modelling in the registration and restoration of a megalithic tomb ABSTRACT: This article aims at showing some potential applications of geomatics to works in which both excavation and restoration are carried out simultaneously, so that the three-dimensional layout of the monument undergoes continuous and important changes throughout the intervention.
The article offers an overview of several works in geometric documentation and three-dimensional modelling carried out during the archaeological excavations and the restoration of a megalithic monument -dolmen Alto de la Huesera- from 2010 to 2014.
The activities described here encompass a wide range of goals, including marking out the excavation grid, the geometric recording of the burials, the three-dimensional modelling of the slabs and the surrounding mound, the virtual visualization and check of possible reconstructions before undertaking actual rearrangements of the components on site as well as the classification and archive of the information so as to maintain the traceability of the tasks accomplished during this period. NATURAL dolmen, stereoplotting, Structure from Motion (SfM), incremental 3D model, KEYWORDS: multitemporal 3D model (4D model) CONTROLLED (From the UNESCO’s thesaurus [http://databases.unesco.org/thesaurus/]) KEYWORDS: Cultural Heritage, Restoration, Prehistory, Photogrammetry, Computer Graphics
Publicación / Publication Comunicación en un congreso / Lecture in a congress NOMBRE: Geores 2017. Geomatics and restoration :NAME LUGAR: Florence (Italy) :PLACE FECHA: 22-24 May 2017 :DATE ACTAS: The International Archives of the Photogrammetry, Remote Sensing :PROCEEDINGS and Spatial Information Sciences, Volume XLII-5/W1, 2017
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pp. 297-304 FECHA: 2017 :DATE WEB: http://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XLII-5- :WEB W1/297/2017/ NOTAS: :NOTES Artículo en revista / Journal paper NOMBRE: :NAME EDITOR: :EDITOR NÚMERO: :NUMBER FECHA: :DATE ISBN: :ISBN ISSN: :ISSN WEB: :WEB PÁGINAS: :PAGES NOTAS: :NOTES Otro / Other DETALLES: :DETAILS DOI: http://dx.doi.org/10.5194/isprs-archives-XLII-5-W1-297-2017 :DOI
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Cita completa recomendada / Recomended full citation CITA: RODRÍGUEZ MIRANDA Álvaro, PÉREZ VIDIELLA Pablo, :CITATION FERNÁNDEZ-ERASO Javier, MUJIKA-ALUSTIZA Jose Antonio, VALLE MELÓN José Manuel. 2017. 3D Modelling in the registration and restoration of a megalithic tomb. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. XLII-5/W1: 297-304 (doi: http://dx.doi.org/10.5194/isprs-archives-XLII- 5-W1-297-2017)
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy
3D MODELLING IN THE REGISTRATION AND RESTORATION OF A MEGALITHIC TOMB
Á. Rodríguez Miranda a, P. Pérez Vidiella a, J. Fernández-Eraso b, J.A. Mujika-Alustiza b, J.M. Valle Melón a *
a Laboratory for the Geometric Documentation of Heritage (GPAC - Built Heritage Research Group) – University of the Basque Country (UPV/EHU), Vitoria-Gasteiz (Spain) – [email protected] b Dept. of Geography, Prehistory and Archaeology – University of the Basque Country (UPV/EHU), Vitoria-Gasteiz (Spain) - [email protected], [email protected]
Commission VI, WG VI/4
KEY WORDS: dolmen, stereoplotting, Structure from Motion (SfM), incremental 3D model, multitemporal 3D model (4D model)
ABSTRACT:
This article aims at showing some potential applications of geomatics to works in which both excavation and restoration are carried out simultaneously, so that the three-dimensional layout of the monument undergoes continuous and important changes throughout the intervention. The article offers an overview of several works in geometric documentation and three-dimensional modelling carried out during the archaeological excavations and the restoration of a megalithic monument -dolmen Alto de la Huesera- from 2010 to 2014. The activities described here encompass a wide range of goals, including marking out the excavation grid, the geometric recording of the burials, the three-dimensional modelling of the slabs and the surrounding mound, the virtual visualization and check of possible reconstructions before undertaking actual rearrangements of the components on site as well as the classification and archive of the information so as to maintain the traceability of the tasks accomplished during this period.
1. INTRODUCTION simultaneous display of models representing different times will be problematic due to the fully three-dimensional rearrangement As is well known, “restoration” implies the modification of the of the scene. shape, the displacement of the components and changes to the appearance of the elements of heritage that undergo works. For More specifically, we refer to the excavation and restoration their part, the techniques for massive data capture (such as works that, throughout five campaigns (from 2010 to 2014), photogrammetry or laser scanning) allow for the generation of were done at a megalithic tomb -dolmen of Alto de la Huesera, detailed three-dimensional models that show the state of the located near the town of Laguardia (Álava, Spain), in monument at different moments, which enables us not only to coordinates 42º34’10” N, 2º33’58” W-. This construction can register each state but also to analyse the changes over time. be dated to the end of the Neolithic or even to the Early Chalcolithic period (between 4200 and 3500 BC), remaining in These changes can be interpreted from two complementary use until the Intermediate Bronze Age (Fernández Eraso; points of view: on the one hand, they make possible to know the Mujika Alustiza 2013a). Originally, the dolmen comprised a extent of the interventions and executed works during the chamber of around 3 x 3 metres in plan view made up by six restoration process (material removal, reconstruction, etc.), thus large slabs up to 3 metres high with another big stone as cover recording the tasks performed by the different professionals on top. This chamber was accessible through a corridor formed who are working on site; on the other hand, if it is the case that by two parallel lines of smaller vertical slabs, the complete each three-dimensional model can be linked to a specific structure being buried under a circular mound. This passage historical significance, the sequence of models will reproduce tomb was identified in 1947 by Fernández Medrano (Fernández the development of the element of heritage over time. Medrano, 1948; Barandiaran & Fernández Medrano, 1959), who excavated the polygonal chamber during the following The simplicity of the analyses of the changes in the visible year. appearance of an element of heritage through a series of three- dimensional models will be determined by the characteristics As told before, from 2010 onwards a new series of excavations and the nature of the interventions themselves. For instance, over the entire site allowed its demarcation, defined the limits of when we deal with an archaeological excavation, the process of the burial mound -of around 22 metres in diameter- and brought digging itself makes the successive levels progressively deeper, to the surface an 8 metres long corridor (Fernández Eraso; in such a way that they all can be represented by means of easily Mujika Alustiza 2011, 2012, 2013b, 2014). During the understandable stratigraphic columns. On the contrary, there are excavations, the remains of around 130 individuals were other cases –such as the subject of this article- in which the exhumed. Among the recovered materials, artifacts such us an
* Corresponding author
This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-297-2017 297 The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy
abruptly retouched trapezium, ten arrowheads with bifacial Clottes, 1970; Beguiristain, 2007-2008; Orengo, 2013; Gavilán plane finishing touches of different morphology, one bronze et al., 2013; Schmitt & Bizot, 2016). Additionally, there are arrowhead and one bronze graver, as well as some less woks providing integrated studies of megaliths from different characteristic pieces (such as one polished stone axe, several perspectives (López & Mañana, 2013). lithic flakes –one sickle-, etc.) stand out. As for the pottery, Bell Beaker incise-printed shards and more than one hundred beads The documentation of the monuments is a common procedure can be highlighted. before undertaking any kind of work which might modify their appearance (Mañana, 2005; Aboal & Porto, 2012; Corton et al., 2013), both as a record of the previous form of the site and as 2. OBJECTIVES part of the background information for the planning of the restoration itself. The geometric modelling of the megaliths is The aims that geomatics covered in this project included: also useful for the study of their structural stability (Navarro et al., 2008; Reinosa & Romera, 2015), the visualization of the a. Establishing a reference network in an absolute hypothesis concerning the construction process and their coordinate system. appearance in ancient times (López de Calle et al., 2001; b. The stakeout of the excavation grid. Bouillon & Cassen, 2008; Luján & Aguilella, 2012; Ledo, c. The documentation and mapping of the material and 2016), the musealization on-site (Gutiérrez, 2008) as well as the skeletal remains found during the excavations. generation of contents for the interactive 3D visualization and d. Three-dimensional virtual modelling of the state of the dissemination via new digital technologies (Caro & Hansen, the site and the visible structures at different times 2015). and the generation of different outputs such as plan views, elevations, perspectives, cross-sections, etc., 3.2 Documentation of the Alto de la Huesera megalithic which can represent the accomplished works and tomb assist the task planning for the next steps. e. The generation of an incremental three-dimensional In the year 2010 –before the intervention- the remains of the model that allows assessing the evolution of the mound looked like a haphazardly deposit of debris, among works yearly. which only the top of the slabs of the chamber and the cover f. Visualizing hypotheses of the original appearance of (fallen and thrust inside) stood out slightly (see figure 1). the monument. During the campaigns of study of the site, the excavation works g. The archive of the information in order to maintain overlapped with the refurbishment. As a result, while the the traceability of the generated products, thus chamber, the corridor and the mound were being uncovered, permitting their re-use over time. different actions were performed which led to the installation or the removal of reinforcement elements, the stockpile and transport of materials, the dismantlement of some parts of the In particular, the three-dimensional models mentioned in points monument and the reconstruction of other parts. “d”, “e” and “f” of the list above are addressed in further detail in the following sections of the text. For these models, the different techniques used for their production as well as the applications of each type are discussed.
3. DEVELOPMENT
3.1 Geomatics for the geometric documentation of dolmens
Prehistoric megalithic constructions have attracted attention from many points of view and scales of study, which has resulted in the application of a large repertoire of techniques of geometric documentation (surveying with total station, laser scanning, photogrammetry, etc.).
For example, we can find studies concerning their astronomic orientation (Hoskin, 2009; Lozano et al., 2014); their relationship with the landscape and the perception of the Figure 1. Image of the dolmen in 2010, before undertaking the territory (Criado & Mañana, 2003; Enríquez & Duque, 2015); new series of excavations. the characteristics of the burial mound (Arnal & Balsan, 1980; Moraza et al., 2003; De Blas, 2006; Blanco & Fabian, 2011); the arrangement of the slabs making up the chamber and the corridor (Baceiredo & Baceiredo, 2012; Martínez-Torres et al., The initial project of geometric documentation used 2014; Benavides et al., 2016); the degradation of the materials photogrammetric pairs (figure 2), which were subsequently due to atmospheric causes or biodeterioration (Romão & stereoplotted generating a three-dimensional wireframe model Rattazzi, 1996; Figueiredo et al., 2008); the documentation and (figure 3), and, in a second step, a model of quadrangular analysis of the engravings and remains of paintings (Bueno et meshes (figure 4). In addition, from these three-dimensional al., 2007; Cassen et al., 2014; Cortón et al., 2015); the models new products such as plan views or cross-sections were archaeological excavations and the documentation of the derived. This approach was laborious since it required the exhumed remains, both artefacts and burials (Carrière & orientation of the stereopairs and the manual drawing
This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-297-2017 298 The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy
(meaningful lines and arrays of points defining the surfaces) by For its part, the intervention period coincided in time with a an operator, as well as the individual meshing of the surfaces significant progress in the three-dimensional modelling and the edition of each component of the three-dimensional techniques, namely the market entry –from the year 2012 model. However, at that time, this procedure was deemed approximately- of many pieces of software based on SfM adequate given that the slabs of the dolmen were braced with (Structure from Motion) algorithms, with the consequent steel support props and wooden planks (elements that we did simplification of the procedures for the generation of 3D models not want to include in the 3D model), and because of the from photographs, the greater level of detail of the results and existence of hidden areas and nooks, in which supervised the possibilities given by the automatic texture mapping options drawing permits avoiding the undesired elements, filling the and their derivatives such as the orthoimages (figure 5). Around gaps and tracking the quality of the results. that time, the areas to be documented at the dolmen did no longer include the chamber (whose geometry was not particularly appropriate for SfM processing). Instead, the works focused on the open spaces of the corridor and the upper surface of the mound, which could be documented with a suitable geometry of the shots and within a short period of time (approximately 1 hour to take enough photographs for the complete surface of the mound) by the combination of images taken at ground level and oblique shots with a 4.5 metres high pole (figure 6).
Figure 2. Photogrammetric record by means of stereopairs of the cover slab after its removal from the chamber (July 2010).
Figure 5. Orthoimage with the line drawing of some relevant archaeological structures superimposed. The layout also shows the excavation grid (1x1 m) and some hypotheses regarding the original extend of the burial mound.
Figure 3. Stereoplotting (line drawing) of a photogrammetric pair.
Figure 6. Photographic record (for convergent photogrammetry) of the site from an elevated point of view by means of a camera placed at the top of a pole (year 2014). Figure 4. Model of surfaces (January 2011, before the replacement of the cover slab). The size of the meshes is different for the constructive elements (3 cm) and for the Anyway, with the aim of maintaining the continuity of the 3D representation of the barrow (20 cm). models of the successive campaigns with the initial one, we carried on taking stereoscopic pairs for every phase, which were
This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-297-2017 299 The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy
also orientated and drawn. Indeed, the 3D model generated by SfM techniques were also useful for adding to the 3D model the stereoplotting has some interesting features which indicate that information on the burials excavated inside the chamber and the this technique is applicable in spite of its “handmade” character. corridor. For the documentation of the excavations in these For example, the resulting models are rather light and, areas, the participation of the surveyors was not considered moreover, both meshes and lines can be easily classified so as to from the beginning; this is why only sketches and some sparse individualize the different components of the monument. Thus, photographs were available as geometric documentation. In this for each new campaign only the changes with respect to the case, by taking the photographs from the archaeological record previous one needed to be drawn, thereby generating an and using as reference points the marks of the excavation grid incremental three-dimensional model. This multitemporal and other elements visible on the pictures -such as ranging model lacks photographic texture (unlike the models generated poles or the lower part of the slabs-, it was possible to generate by SfM). Nevertheless, conventional CAD software handles it a series of partial 3D models (figure 8) from which orthoimages effortlessly and it is well suited to be used for the design of the were generated in turn. These orthoimages were inserted in the following restoration steps in which, for instance, the slabs are CAD model and, then, the perimeters of the bones and the virtually relocated according to different alternatives (figure 7). material findings were outlined (figure 9).
Figure 8. Partial 3D model generated from the pictures taken during the excavation of the burials (software Autodesk 123D- Catch®).
Figure 7. Virtual models showing the evolution of the site. Above, in 2010 with the stone of the cover removed from the chamber before the excavations. Below, in 2014, with the cover stone replaced on top of the chamber and the barrow partially dismantled.
Indeed, stereoscopy and convergent processing are not incompatible. If needed in the future, as long as the overlap of the stereopairs is large (e.g. 80%) and care is taken in having varied orientations for the shots –thus providing better intersection angles for the convergent processing-, they could be reprocessed in order to generate three-dimensional models with photographic textures with SfM software (Rodríguez et al., 2015). Although such overlaps are unnecessary for Figure 9. Drawing of the skeletal remains, together with the stereoplotting (where values of 60% are enough), photographs can be taken in a quick and inexpensive manner nowadays, with outline of the slabs (the cover is not represented in order to which it is not a problem to dispose of an overabundance of make the layout clearer). Colours identify bones visible at pictures that we will keep for archival purposes and future re- different times of the excavation. uses, even if, at first, we use only a selection for line drawing.
This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-297-2017 300 The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy
This work was time-consuming since the skeletons did not lay line maps and obtaining dissemination products in clearly differentiated strata but they appeared in a continuous (figure 12). layer in which the different remains of the individuals were superimposed. As a result, it was difficult to take series of photographs showing exactly the same moment of the excavation –without changes in the arrangement of the scene- large enough to be computed by means of SfM techniques. In total, ten partial 3D models were generated with the aim of giving a complete coverage of the excavated area both in extension and stratigraphy.
4. RESULTS
As has been said in the previous sections, the results of this research include:
1. The collection of registers, that is to say, the photographs gathered in stereoscopic pairs and groups for convergent processing concerning each campaign. Pictures were conveniently classified and their Figure 11. Three-dimensional model with photographic textures descriptions enriched with Exif and IPTC metadata (year 2014). Perspective rear view with the indication of a (Valle & Rodríguez, 2010), thus allowing for a better contour line limiting the part of the barrow above the floor of information management. the corridor.
2. Three-dimensional wireframe CAD model –3D lines and surfaces without texture- obtained by means of stereoplotting of the photogrammetric pairs, digitization over the orthoimages and direct capture with the total station. In this model, elements are classified and form a single incremental set which guarantees the recreation of the different moments of the excavation, as well as the virtual modification of the position of the elements in order to visualize hypotheses regarding the original arrangement of the slabs or planning restoration works. From this 3D Figure 12. Red-cyan anaglyph of a top view of the corridor, model, different kinds of outputs such as plan views, cross sections, perspective views of developments generated from the 3D model with photographic texture. (figure 10) have been generated.
5. DISCUSSION
Although not directly related to the survey work, it is worth mentioning that, at the end of the referred period, important disagreements arose between the archaeologists and the administration in charge of the maintenance of the monument regarding the final appearance of the megalith once reconstructed. In this conflict, historical and scientific values Figure 10. Example of outcome from the multitemporal meshed collided with the interests of giving an aesthetical appearance and ensuring the safety of the structure. model: development of the slabs which form the chamber after their projection on a cylinder with a diameter of 3 metres. Light This situation highlighted the importance of the documentation colour represents the visible parts at the beginning of the works, as the only way to reinterpret an archaeological site once its whereas full colours show the parts discovered during first configuration has changed completely. year’s excavations. Moreover, whilst it is true that only one option can be chosen for the physical reconstruction of the site, three-dimensional virtual models are a powerful tool for showing alternative 3. A sequence of models with photographic texture and/or augmented versions, including the evolution over time. generated by means of convergent photogrammetry (SfM), representing the different appearances of the site at each stage of the simultaneous processes of 6. CONCLUSIONS excavation and restoration. Apart from the use for three-dimensionally visualizing the site at any given To summarize, this article has dealt with the applicability of moment (figure 11), these models are the basis for the series of three-dimensional models for the monitoring of the generation of orthoimages that can be added to the excavation and restoration works by focusing on the specific
This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-297-2017 301 The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy
case of a megalithic tomb. The main topics of the article include Barandiaran, J.M.; Fernández Medrano, D. 1959 Excavaciones the selection of the most suitable techniques for the geometric en Álava. Boletín de la Institución Sancho el Sabio, año III, documentation as well as the need (and the challenge) to Tomo III, Nº1-2. maintain the continuity of the sequence of models in such a way that it encompasses the whole duration of the works or the Benavides, J.A.; Aranda, G.; Sánchez, M.; Alarcón, E.; progressive incorporation of new technological possibilities in Fernández, S.; Lozano, A.; Esquivel, J.A., 2016. 3D modelling projects for several years. in archeology: the application of Structure from Motion methods to the study of the megalithic necrópolis of Panoria A comparison has also been made between the 3D models with (Granada, Spain). Journal of Archaeological Science: Reports, photographic textures that can be generated quickly and in an 10, pp. 495-506. efficient way by means of techniques of convergent (doi: http://dx.doi.org/10.1016/jasrep.2016.11.022) photogrammetry and the models obtained through the intervention of an operator (in this case using stereoplotting). Beguiristain, M.A., 2007-2008. Un singular acondicionamiento del espacio interno en el dolmen de Aizibita (Cirauqui, Production time and cost are favourable factors for the former, Navarra). Veleia, 24-25(2), pp. 703-722. while it offers a realistic view of the elements thanks to the incorporation of photographic texture, which also permits to Blanco, A.; Fabián, J.F., 2011. ¿Monumentos evocativos? Los generate derivatives of great interest (e.g. orthoimages). túmulos de Los Tiesos (Mediana de Voltoya, Ávila) en su Nevertheless, the models generated automatically by SfM are contexto prehistórico. Munibe (Antropología-Arkeologia), 62, not interpreted. Therefore, although several of them can be pp. 251-282. visualized simultaneously, the comparisons that can be done are limited, to a great extent, to the visual analysis or the realization Bouillon, C.; Cassen, S., 2008. De l’Airbus A380 au site of some basic geometric calculations (such as computing the néolithique de la Table des Marchands (Morbilan): limites et distances between models). On the contrary, in the model perspectives d’un transfert de technologie. Archéovision, 3, pp, generated through stereoplotting, each construction element 158-164. appears individualized, which allow us to process them, for instance, by selecting the parts selected for visualization in the Bueno, P.; de Balbín, R.; Barroso, R., 2007. Chronologie de virtual environment or the prospective appearance of the l’art mégalithique ibérique: C14 et contextes archéologiques.. monument following the rearrangement of the slabs. L’Anthropologie, 111, pp. 590-654. (doi: http://dx.doi.org/10.1016/j.anthro.2007.07.006) These considerations also apply to any model generated automatically, regardless of whether it has been created by Caro, J.L.; Hansen, S., 2015. De la fotogrametría a la difusión means of SfM or through another technique (for example, laser del patrimonio arqueológico mediante game engines: Menga un scanning). The same goes for the interpreted model that, in this caso de estudio. VAR (Virtual Archaeology Review), 6(12), pp. case, was generated through stereoplotting but that, in other 58-68. (doi: http://dx.doi.org/10.4995/var.2015.4159) cases, can be obtained, for instance, by using a BIM (Building Information Modelling) approach. Carrière, M.; Clottes, J., 1970. Le dolmen du Pench nº 1 à Alvignac (Lot). Gallia préhistoire, 13(1), pp. 109-149.
7. ACKNOWLEDGEMENTS Cassen, S.; Lescop, L.; Grimaud, V.; Robin, G., 2014. Complementarity of acquisition techniques for the The excavations were funded by the Diputación Foral de Álava- documentation of Neolitic engravings: lasergrammetric and Arabako Foru Aldundia and were part of the activities of the photographic recording in Gravrinis passage tomb (Brittany, Research Group IT622-13, recognised by the Basque France). Journal of Archaeological Science, 45, pp. 126-140. Government. (doi: http://dx.doi.org/10.1016/j.jas.2014.02.019)
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